It is easy to feel scared and powerless in the wake of attacks like those at the Boston Marathon. But it also plays into the perpetrators' hands.

As the details about the bombings in Boston unfold, it'd be easy to be scared. It'd be easy to feel powerless and demand that our elected leaders do something—anything—to keep us safe.

It'd be easy, but it'd be wrong. We need to be angry and empathize with the victims without being scared. Our fears would play right into the perpetrators' hands—and magnify the power of their victory for whichever goals whatever group behind this, still to be uncovered, has. We don't have to be scared, and we're not powerless. We actually have all the power here, and there's one thing we can do to render terrorism ineffective: Refuse to be terrorized.

It's hard to do, because terrorism is designed precisely to scare people—far out of proportion to its actual danger. A huge amount of research on fear and the brain teaches us that we exaggerate threats that are rare, spectacular, immediate, random—in this case involving an innocent child—senseless, horrific and graphic. Terrorism pushes all of our fear buttons, really hard, and we overreact.

But our brains are fooling us. Even though this will be in the news for weeks, we should recognize this for what it is: a rare event. That's the very definition of news: something that is unusual—in this case, something that almost never happens.

Remember after 9/11 when people predicted we'd see these sorts of attacks every few months? That never happened, and it wasn't because the TSA confiscated knives and snow globes at airports. Give the FBI credit for rolling up terrorist networks and interdicting terrorist funding, but we also exaggerated the threat. We get our ideas about how easy it is to blow things up from television and the movies. It turns out that terrorism is much harder than most people think. It's hard to find willing terrorists, it's hard to put a plot together, it's hard to get materials, and it's hard to execute a workable plan. As a collective group, terrorists are dumb, and they make dumb mistakes; criminal masterminds are another myth from movies and comic books.

Even the 9/11 terrorists got lucky.

If it's hard for us to keep this in perspective, it will be even harder for our leaders. They'll be afraid that by speaking honestly about the impossibility of attaining absolute security or the inevitability of terrorism—or that some American ideals are worth maintaining even in the face of adversity—they will be branded as "soft on terror." And they'll be afraid that Americans might vote them out of office. Perhaps they're right, but where are the leaders who aren't afraid? What has happened to "the only thing we have to fear is fear itself"?

Terrorism, even the terrorism of radical Islamists and right-wing extremists and lone actors all put together, is not an "existential threat" against our nation. Even the events of 9/11, as horrific as they were, didn't do existential damage to our nation. Our society is more robust than it might seem from watching the news. We need to start acting that way.

How well this attack succeeds depends much less on what happened in Boston than by our reactions in the coming weeks and months. Terrorism isn't primarily a crime against people or property. It's a crime against our minds, using the deaths of innocents and destruction of property as accomplices. When we react from fear, when we change our laws and policies to make our country less open, the terrorists succeed, even if their attacks fail. But when we refuse to be terrorized, when we're indomitable in the face of terror, the terrorists fail, even if their attacks succeed.

Don't glorify the terrorists and their actions by calling this part of a "war on terror." Wars involve two legitimate sides. There's only one legitimate side here; those on the other are criminals. They should be found, arrested, and punished. But we need to be vigilant not to weaken the very freedoms and liberties that make this country great, meanwhile, just because we're scared.

Empathize, but refuse to be terrorized. Instead, be indomitable—and support leaders who are as well. That's how to defeat terrorists.